Immunoassay technologies are widely used in the field of medical diagnostics. One example of a commercially used immunoassay is the induced luminescence immunoassay (LOCI®) technology. The induced luminescence immunoassay is described in U.S. Pat. No. 5,340,716 (Ullman), the entire contents of which are expressly incorporated herein by reference. The currently available LOCI® technology involves a homogeneous assay (i.e., no wash steps involved) that has high sensitivity, and the assay uses several reagents and requires that two of these reagents (referred to as a “sensibead” and a “chemibead”) held by other immunoassay reagents to be in close proximity to achieve a signal. Upon exposure to light at a certain wavelength, the sensibead releases singlet oxygen, and if the two beads are in close proximity, the singlet oxygen is transferred to the chemibead; this causes a chemical reaction that results in the chemibead giving off light that can be measured at a different wavelength.
However, there are obstacles that exist for this technology. There are multiple factors that can contribute to background signal, such as but not limited to, (1) the nonspecifically binding of two beads to one another, and (2) the presence of two unattached beads that are simply in close proximity to one another. For these reasons, the final reaction mixture is diluted prior to light exposure to dissociate nonspecifically bound beads and to increase the mean particle distance between unbound beads. In addition, as the assay is homogeneous, plasma separation is required, and thus whole blood cannot be directly used in this diagnostic platform.
The presently disclosed and claimed inventive concept(s) is directed to new and improved compositions, assays, and methods of use thereof; this technology provides a heterogeneous assay format in which background signal is reduced or eliminated and plasma separation is not required.